Ambassador Samantha Power urged Djotodia to "ensure the arrest of perpetrators of recent atrocities," urging him to denounce violence and call for an immediate return to law and order, her office said yesterday.
Power also asked Djotodia to "use his influence to reduce inter-religious tensions and protect civilians" and to give "full support" to French and African Union forces that are deploying to the Central African Republic.
Hundreds have died in a fresh outbreak of bloodshed in the Central African Republic, which has been in turmoil since a coalition of Muslim fighters led by Djotodia known as the Seleka overthrew the country's leader Francois Bozize in March.
Although Djotodia disbanded the Seleka, some militiamen went rogue and warlords soon imposed a reign of terror on large swathes of land.
Local Christians responded by forming vigilante groups and the government was never able to assert its authority over the sprawling, landlocked country.
Reports have described a series of horrors, with security forces and militia gangs razing villages, carrying out public killings and perpetrating widespread rapes.